Purpose
The purpose of this project is to provide a series of four calculators that will allow you to easily get an approximation of:

How many gallons of water per square foot and one acre are received annually by entering the number of inches of annual rainfall

How many gallons of water per square foot and one acre you need to offset to water plants / trees that are not native to your geographic region

How many gallons of water per square foot you need to offset in order to water plants / trees that are not native to your geographic region when you know the horizontal length of the root system

I created these calculators because I was growing tired of reading generalizations of "water often" and "do not over water" (among other mystifying phrases) that commonly come with plants, seeds and trees. I don't know about you, but when I buy a plant I'm more interested in how many gallons of water I need to supply that plant versus a mysterious phrase.

Granted, these calculators do not take into account the differences between soil types (between where you live and where the plant or tree is native to) and elevation, but the following calculators can help you eliminate a lot of guess-work. By helping you eliminate guess-work, you'll have a much better idea how how much water your plants or trees may require in your geographic region.

If you do not know what the annual rainfall (in inches) is for your geographic region or another geographic region, usually you can find a web site which will have the number by searching using terms such as "inches annual rainfall las vegas nevada".

Finally, these calculators may prove to be useful if you have wondered how much water you would need to capture and store to provide yearly water to plants, trees or crops. Some areas may have restrictions on capturing water so, to be safe, check first.

#1 - Calculate How Many Gallons Of Annual Rainfall A Geographic Region Receives : Enter Number

Get Your Own Sequoia.I did.

This calculator is useful when you need to determine how many gallons of annual rainfall are received by soil for a specific geographic region. With this calculator you will need to know how many inches of annual rainfall a geographic region receives per year.

Enter the number of inches of annual rainfall received

Press this button to have the calcuation answers shown below

0.0775

Gallons of water received weekly by one square foot of soil

0.31

Gallons of water received monthly by one square foot of soil

3.7199999999999998

Gallons of water received annually by one square foot of soil

162912

Gallons of water received annually by one square acre of soil

#2 - Calculate How Many Gallons Of Annual Rainfall A Geographic Region Receives : Select Location
This calculator is useful when you need to determine how many gallons of annual rainfall are received by soil for a general geographic region. If you know the annual rainfall amount in inches for a specific geographic location, use the first calculator.

Select general geographic region with annual rainfall recorded

Press this button to have the calcuation answers shown below

0.10165416666666667

Gallons of water received weekly by one square foot of soil

0.4066166666666667

Gallons of water received monthly by one square foot of soil

4.8794

Gallons of water received annually by one square foot of soil

213686.24

Gallons of water received annually by one square acre of soil

#3 - Calculate How Many Gallons Of Annual Rainfall You Need To Offset : Simple

Get Your Own Sequoia.I did.

This calculator is useful when you need to determine how many gallons of annual rainfall that you must take from a water source in order to simulate the annual rainfall of a different geographic region. For example, if you live in Las Vegas, Nevada (average of 4 inches of annual rainfall) and you are trying to grow a Giant Sequoia that normally occurs around San Francisco, California (average of 20 inches of annual rainfall), this will calculate the number of gallons that are needed in your location (Las Vegas, Nevada in this example) for the Giant Sequoia.

Enter the number of inches of annual rainfall you receive

Enter the number of inches of annual rainfall from the geographic region the plant or tree normally lives in

Press this button to have the calcuation answers shown below

0.20666666666666667

Gallons of water needed weekly by one square foot of soil

0.8266666666666667

Gallons of water needed monthly by one square foot of soil

9.92

Gallons of water needed annually by one square foot of soil

434432

Gallons of water needed annually by one square acre of soil

#4 - Calculate How Many Gallons Of Annual Rainfall You Need To Offset : Root System
This calculator is useful when you need to determine how many gallons of annual rainfall that you must get from a water source in order to simulate the annual rainfall of a different geographic region. For example, if you live in Las Vegas, Nevada (average of 4 inches of annual rainfall) and you are trying to grow a Giant Sequoia that normally occurs around San Francisco, California (average of 20 inches of annual rainfall), this will calculate the number of gallons that are needed in your location (Las Vegas, Nevada in this example) for the Giant Sequoia.

Unlike the previous calculator, this will calculate the number of gallons of water needed based on the horizontal length of a plant or tree's root system. For example, if you know the horizontal length of a Giant Sequoia's roots spread out 100 feet horizontally on one side (this is known as the radius of a circle in geometry) from the trunk of the tree, enter that number.

Enter the number of inches of annual rainfall you receive

Enter the number of inches of annual rainfall from the geographic region the plant or tree normally lives in

Enter the horizontal radius of the plant or tree root system in feet

Press this button to have the calcuation answers shown below

6489.333333333333

Gallons of water needed weekly for the soil area with a radius of 100 feet around the plant / tree (15700 total square feet)

25957.333333333332

Gallons of water needed monthly for the soil area with a radius of 100 feet around the plant / tree (15700 total square feet)

311488

Gallons of water needed annually for the soil area with a radius of 100 feet around the plant / tree (15700 total square feet)

Constants Used By Calculators

43,560

Square feet comprise one acre

27,152

Gallons of rainwater falls on one square acre of land when 1 inch of rain is measured

0.62

Gallons of rainwater falls on one square foot of land when 1 inch of rain is measured